1. Technical Field
The present invention relates to a time measurement device including a reciprocating hand.
2. Related Art
Chronograph timepieces that display not only the current time but also measure the time to display the measured time have been known. Some of the chronograph timepieces indicate a value of sub-second digit of the measured time using a reciprocating hand (see, for instance, Patent Literature 1: JP-A-2013-29400, and Patent Literature2: JP-A-2007-256066).
An electronic timepiece disclosed in Patent Literature 1 uses a reciprocating 1/10 second hand to indicate 1/10 second. The movement direction of the hand is reversed every 0.5 seconds. The hand indicates seconds in a range from 0 to 0.5 seconds when the hand is on a forward route, while the hand indicates seconds a range from 0.5 to 1.0 seconds when the hand is on a return route. Positions to be pointed by the 1/10 second hand of the electronic timepiece are shifted from positions pointed to be pointed on the forward route so that whether the 1/10 second hand is on the forward route or on the return route can be recognized even when the 1/10 second hand is stopped after the time measurement. Accordingly, 1/10 second graduations provided around a movement area of the 1/10 second hand include forward-route indexes (i.e. indexes for indicating 0 to 0.5 seconds) and return-route indexes (i.e. indexes for indicating 0.5 to 1.0 seconds) that are mutually shifted so as not to be overlapped in the pointing direction of the hand.
An electronic chronograph timepiece disclosed in Patent Literature 2 uses a reciprocating hand to indicate 1/20 seconds. The hand indicates the measured time (0/20 to 19/20 seconds) only in a forward route. Then, the hand of the electronic chronograph timepiece returns to an initial position (0/20 second position) on the return route.
The electronic timepiece disclosed in the Patent Literature 1 entails a problem that, when the display area of the 1/10 second graduations is small, intervals between the forward-route indexes and the return-route indexes cannot be sufficiently secured, so that it is difficult to determine which of the forward-route indexes and the return-route indexes are pointed by the 1/10 second hand.
The electronic chronograph timepiece disclosed in Patent Literature 2 requires a time lag for returning the hand to the initial position (i.e. a time for returning the hand from 19/20 second position to 0/20 second position), so that the time indicated by the hand cannot always be the same as the measured time. Accordingly, when the time indicated by the hand is not the same as the measured time when the measurement is completed, it is necessary to move the hand to the position indicating the measured time, so that the measured time cannot be immediately recognized.